O.4.8.3 Transient Acoustic Signatures of the GreenHP with special focus on icing and defrosting
In the framework of the EU project GreenHP a new air-water-heat pump using the natural refrigerant propane is developed. A new compressor concept, heat exchangers produced out of aluminium microchannels attached to efficient air fin structures and a specialized fan have been implemented. The acoustic behaviour is characterized setting a special focus on transient effects during icing and defrosting. For this purpose, a 64-channel acoustic dome is positioned around the heat pump in the climate chamber to acquire space-, time- and frequency resolved microphone data. Measurements are performed for different acoustic shielding of the heat pump. The resulting acoustic directivity and its variation during frosting is correlated to fluid flow and ice aggretion measurements: laser optical methods (particle image velocimetry) and probe techniques (constant temperature anemometry) are used to measure the air velocity both at the air inlet and in the gap between heat exchanger and fan. Computational fluid mechanics is performed to simulate the frosting behaviour based on the measured boundary conditions. For accessing the ice amount a local measuring method is applied based on the fact, that the heat exchanger in the GreenHP is positioned horizontally: Below the heat exchanger area, 180 boxes are positioned gathering the water during defrosting. The local ice amount is compared to the simulation results, which are correlated to the acoustic data. Providing these toolsets for development of low noise signature air-to-water heat pumps is important for increasing acceptance of this technology.